Medical pressure-sensitive adhesive composition, process for producing the same, and medical tape

ABSTRACT

A medical pressure-sensitive adhesive composition having excellent re-adhesion property, and also excellence in both the peel adhesion property and the low skin stimulus property, a process for producing the same, and a medical tape are provided. In the medical tape, a medical pressure-sensitive adhesive composition containing acrylic polymer and acrylic oligomer is laminated on a substrate, wherein the medical pressure-sensitive adhesive composition is prepared by cross-linking an intermediate composition containing an acrylic polymer having a cross-linkable functional group and an acrylic oligomer containing 10 to 40 percent by mole of vinyl monomer with a lactam ring through the use of a cross-linking agent, and wherein this medical tape is made by compounding the acrylic oligomer in the range of 50 to 700 parts by weight relative to 100 parts by weight of acrylic polymer, while the number average molecular weight of the acrylic polymer is set at a value within the range of 300,000 to 1,500,000, and the number average molecular weight of the acrylic oligomer is set at a value within the range of 1,000 to 10,000.

TECHNICAL FIELD

The present invention relate to a medical pressure-sensitive adhesivecomposition, a process for producing the same, and a medical tape(adhesive tape). In particular, it relates to a medicalpressure-sensitive adhesive composition having excellent re-adhesionproperty, and also excellence in both the peel adhesion property and thelow skin stimulus property (low skin irritation), although the two aremutually contradictory. Also it relates to a process for producing thesame, and a medical tape.

BACKGROUND ART

Since a medical tape (adhesive tape) which consists of a substrate and amedical pressure-sensitive adhesive composition is used by adhering orwinding itself around the skin (corneous layer), as well as havingmoderate adhesion to the skin; it is preferable to have a proper peelproperty that does not cause skin stimulus or a rash by peeling damageto the corneous layer of the skin.

Therefore, in recent years, the medical pressure-sensitive adhesivecomposition and the medical tape have been proposed in consideration ofa good balance between the skin adhesion property and the peel property.

For example, JP6-4533B(JP62-77316A) has disclosed the externalapplication medicine component in which a polymer alloy is laminated ona substrate, wherein the polymer alloy has a number average molecularweight of 90,000 to 250,000 and the ratio (Mw/Mn) of a weight averagemolecular weight (Mw) to the number average molecular weight (Mn) of 6to 12, and consists of 80 to 99.5 percent by weight of acrylic polymerand 0.5 to 20 percent by weight of acrylic oligomer having a numberaverage molecular weight of 700 to 5,000.

Moreover, JP3-70685B has disclosed the pasting agent in which apressure-sensitive adhesive layer containing a medicament and an(meta)acrylic acid ester-vinyl pyrrolidone random copolymer thatcontains 1 to 60 percent by mole of vinyl pyrrolidone is laminated onone surface of a substrate sheet.

However, each of the external application medicine component has beendisclosed in JP6-4533B and JP3-70685B is substantially a singleformulation, and moreover, because it is not cross-linked, it causes ashortfall of cohesive force or an excessive restriction of theadditional amount of an acrylic oligomer, and the control of thecorneous picking area ratio becomes difficult. Also, the problem of poorre-adhesion property is witnessed, as represented in the result of thecomparison between comparative example 9 and the present invention asshown in FIG. 2. Moreover, since the number average molecular weight ofthe acrylics polymer to be used is low, the problem is witnessed in thatthe cohesive force becomes even more insufficient and the adhesion tothe skin becomes poor.

Therefore, various acrylic adhesive compositions that contain an acrylicacid ester polymer and a liquid component or pasting agents includingthem have been known.

For example, JP5-139960A has disclosed the pasting agent, which has theadhesive layer made from the cross-linked polymer on one side of asubstrate. This pasting agent is characterized by the 180° peel adhesionstrength that is 20 to 180 g/12 mm in width, when the adhesive layer isbonded together. More concretely, this pasting agent contains an acrylicacid ester polymer and a liquid plasticizer which is compatible withthis polymer, as an adhesive layer.

Moreover, JP2971998B (JP5-65460A) has disclosed the acrylic pressuresensitive adhesive sheet which has the maximal moving distance such as0.5 to 6 times of the adhesion layer's thickness due to a sheardeformation under shear stress, which contains acrylic acid esterpolymer and a liquid component, for example, a plasticizer or asurfactant, which is compatible with the acrylic acid ester polymer onat least one surface of a support, and which is an elastic body thatdoes not cause cohesive failure or interface failure when a shear stressis applied.

However, in the acrylic pressure-sensitive adhesive composition and thepasting agent including the same, which have been disclosed in theJP5-139960A and JP2971998B(JP 5-65460A), the problem is witnessed inthat the re-adhesion property is poor, as represented in the result ofthe comparison between comparative example 11 and the present inventionwhich are shown in FIG. 2. More concretely, since the compatibilitybetween the acrylic polymer and the liquid component or a plasticizerthat is added to the acrylic polymer is inadequate, the liquid componentmay migrate to the surface of the adhesion layer, and skin stimulusbecomes high. On the other hand, the problem is witnessed in that properpeel adhesion strength is not obtained when the adhesion is tried again,after adhesion to the skin and peeling off have once been performed.Therefore, to solve the above problems, the inventors of the presentinvention have carried out several experimental studies on medical tapesincluding specific acrylic polymers and specific acrylic oligomers. As aresult, the intermediate composition was prepared in advance; thiscomposition was composed of an acrylic polymer having a predeterminednumber average molecular weight (Mn) including a predetermined amount ofa specific type of acrylic oligomer having a predetermined numberaverage molecular weight (Mn). Then, by crosslinking the intermediatecomposition, it was able to provide a medical tape that had an excellentre-adhesion property and that caused only slight skin stimulus, while atthe same time, the wettability against the skin was kept high, and apredetermined peel adhesion strength was maintained. Consequently, thepresent invention has been completed.

Thus, an objective of the present invention is to provide a medicalpressure-sensitive adhesive composition that is excellent in re-adhesionproperty, while the peel adhesion property is good and skin stimulus islow, to provide a process for producing the same, and to provide amedical tape in which such a medical pressure-sensitive adhesivecomposition is formed on a substrate.

SUMMARY OF THE INVENTION

-   [1] According to the present invention, a medical pressure-sensitive    adhesive composition is provided, in which an intermediate    composition is cross-linked through the use of a cross-linking    agent, wherein the intermediate composition contains an acrylic    polymer having a cross-linkable functional group and an acrylic    oligomer prepared by polymerization of monomers containing 10 to 40    percent by weight of vinyl monomer with a lactam ring, while the    number average molecular weight of the acrylic polymer is set at a    value within the range of 300,000 to 1,500,000, the number average    molecular weight of the acrylic oligomer is set at a value within    the range of 1,000 to 10,000, and the medical pressure-sensitive    adhesive composition is made by compounding the acrylic oligomer in    the range of 50 to 700 parts by weight relative to 100 parts by    weight of acrylic polymer. Consequently, the problem noted earlier    can be solved.

That is, since a specific acrylic oligomer increases the wetting areaagainst the skin, the predetermined peel adhesion strength can beobtained, while a medical pressure-sensitive adhesive compositionexhibiting low skin stimulus and having an excellent re-adhesionproperty can be obtained. Moreover, since the number average molecularweight of the acrylic polymer to be used is comparatively high, and theacrylic polymer is cross-linked, a high cohesive force is obtained, agood compatibility with an acrylic oligomer is exhibited, peel adhesionstrength is easily obtained, and the migration of the acrylic oligomerto the outside from the acrylic polymer can be prevented easily.

-   [2] Also, in the component of the medical pressure-sensitive    adhesive composition of the present invention, it is preferable that    an acrylic polymer having no cross-linkable functional group is    included other than the acrylic polymer having a cross-linkable    functional group, and the additional amount of this acrylic polymer    is set at a value within the range of 1 to 50 percent by weight,    relative to the whole amount of the medical pressure-sensitive    adhesive composition.-   [3] Also, in the component of the medical pressure-sensitive    adhesive composition of the present invention, it is preferable that    the acrylic oligomer contains a (meth)acrylic acid alkyl ester    monomer as a monomer component, and the molar fraction of this    (meth)acrylic acid alkyl ester monomer is set at a value within the    range of 60 to 90 percent by mole relative to the whole amount of    the oligomer.-   [4] Also, in the medical pressure-sensitive adhesive composition of    the present invention, it is preferable that the acrylic oligomer    includes 2-ethylhexylacrylic ester and N-vinyl-2-pyrrolidone as    monomer components.-   [5] Also, in the medical pressure-sensitive adhesive composition of    the present invention, it is preferable to set the viscosity (25°    C.) of the acrylics oligomer at a value within the range of 10 to    1,000 dPa·.-   [6] Also, in the component of the medical pressure-sensitive    adhesive composition of the present invention, it is preferable that    a medicament is included at content within the range of 0.1 to 30    percent by weight relative to the whole amount of medical    pressure-sensitive adhesive composition.-   [7] Moreover, an another embodiment of the present invention is a    process for producing a medical pressure-sensitive adhesive    composition including the following steps (1) to (4);-   (1) a step to prepare an acrylic polymer that has a number average    molecular weight of 300,000 to 1,500,000 and has a cross-linkable    functional group-   (2) a step to prepare an acrylics oligomer which has a number    average molecular weight of 1,000 to 10,000 and in which monomer    components containing 10 to 40 percent by mole of vinyl monomer with    a lactam ring are polymerized-   (3) a step to prepare an intermediate composition by compounding an    acrylic oligomer within the range of 50 to 700 parts by weight    relative to 100 parts by weight of acrylic polymer-   (4) a step to add a cross-linking agent into the intermediate    composition obtained from the step (3) so as to carry out the    cross-linking

Thus, by carrying out the production process in this way, the wettingarea increases against the skin and a predetermined peel adhesionstrength is obtained, while a medical pressure-sensitive adhesivecomposition exhibiting low skin stimulus and having an excellentre-adhesion property is obtained efficiently, since the mixing anddispersion of the acrylic polymer and the acrylic oligomer becomes easyand uniformly.

-   [8] Also, an another embodiment of the present invention is a    medical tape in which a medical pressure-sensitive adhesive    composition is laminated on a substrate, wherein the medical    pressure-sensitive adhesive composition is prepared by cross-linking    an intermediate composition containing an acrylic polymer having a    cross-linkable functional group and an acrylic oligomer prepared by    polymerization of monomers containing 10 to 40 percent by mole of    vinyl monomer with a lactam ring through the use of a cross-linking    agent. This medical tape is made by compounding the acrylic oligomer    in the range of 50 to 700 parts by weight relative to 100 parts by    weight of acrylic polymer, while the number average molecular weight    of the acrylic polymer is set at a value within the range of 300,000    to 1,500,000, and the number average molecular weight of the acrylic    oligomer is set at a value within the range of 1,000 to 10,000.

By constituting the medical tape like this, an excellent wettabilityagainst the skin is exhibited, a predetermined peel adhesion strength isobtained, while the skin stimulus is low, and an excellent re-adhesionproperty is exhibited. Furthermore, since it is easy to relativelyadjust the peel adhesion strength and the cohesive force, the transferof the acrylic oligomer to the backside of the substrate can be easilyprevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram that illustrates the example of the medical tapeaccording to the present invention.

FIG. 2 is a diagram that illustrates re-adhesion property (therelationship between the number of times of the peeling off and themaintenance ratio of the peel adhesion strength).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to each appropriate diagram, the preferred embodiments of themedical pressure-sensitive adhesive composition, the medical tape andthe like according to the present invention will be specificallydescribed.

[First Embodiment]

The first embodiment is a medical pressure-sensitive adhesivecomposition in which an intermediate composition is cross-linked throughthe use of a cross-linking agent, wherein the intermediate compositioncontains an acrylic polymer having a cross-linkable functional group andan acrylic oligomer prepared by polymerization of monomers containing 10to 40 percent by weight of vinyl monomer with a lactam ring, while thenumber average molecular weight of the acrylic polymer is set at a valuewithin the range of 300,000 to 1,500,000, the number average molecularweight of the acrylic oligomer is set at a value within the range of1,000 to 10,000, and the medical pressure-sensitive adhesive compositionis made by compounding the acrylic oligomer in the range of 50 to 700parts by weight relative to 100 parts by weight of acrylic polymer.

1. Acrylic Polymer having a Cross-Linkable Functional Group

(1) Type

As for an acrylic polymer having a cross-linkable functional group, usedin the pressure-sensitive adhesive composition of the present invention,as long as it is a polymer obtained by copolymerization orhomopolymerization of the acrylic monomer containing the vinyl monomerhaving a cross-linkable functional group, the type is not particularlylimited. For example, it is preferable to be an acrylic polymer obtainedby copolymerization of the vinyl monomer functional groups, such ascarboxyl groups or hydroxyl groups and (meth)acrylic acid alkyl esterwith the alkyl group's carbon number of 1 to 14.

The reason for this is the acrylic polymer derived from such a monomercomponent is easily cross linked by an external cross linking agent, soas to improve its cohesive force, and also is mutually dissolved easilywith a specific acrylic oligomer, so that the wetting area can beincreased most effectively Moreover, examples of (meth)acrylic acidalkyl esters with the alkyl group's carbon number of 1 to 14 include(meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid propyl ester, (meth)acrylic acid isopropyl ester,(meth)acrylic acid 2-methoxyethyl ester, (meth)acrylic acid butyl ester,(meth)acrylic acid isobutyl ester, (meth)acrylic acid pentyl ester,(meth)acrylic acid hexyl ester, (meth)acrylic acid octyl ester,(meth)acrylic acid isooctyl ester, (meth)acrylic acid 2-ethylhexylester, (meth)acrylic acid nonyl ester, (meth)acrylic acid isononylester, and (meth)acrylic acid lauryl ester alone or combinations of atleast two thereof.

On the other hand, examples of vinyl monomers having a cross-linkablefunctional group include one of (meth)acrylic acid with carboxyl groups,or (meth)acrylic acid 2-hydroxyethyl ester with hydroxyl groups alone orcombinations of at least two thereof.

Moreover, it is preferable to set the additional amount of compoundingof the above-described monomer at a value within the range of 1 to 15percent by weight the amount of the whole monomer components at the timeof the polymerization.

The reason for this is when the additional amount of compounding of theabove-described monomer becomes less than a value of 1 percent byweight, the cross-linking becomes insufficient and, therefore, the peeladhesion strength to the skin may not be improved. On the other hand, ifthe additional amount of compounding of the above-described monomerexceeds 15 percent by weight, the skin stimulus caused by medicalpressure-sensitive adhesive composition may increase.

Furthermore, as for the acrylic polymer having a cross-linkablefunctional group, it is preferable to include at least one monomercomponent identical with that in the acrylic oligomer, which will bementioned later on.

The reason for this is when the acrylic polymer and the acrylic oligomerare the same type of monomer component like this, the compatibilitybetween the acrylic polymer and the acrylic oligomer improvesremarkably.

(2) Number Average Molecular Weight (Mn)

It is preferable to set a number average molecular weight of acrylicpolymer at a value within the range of 300,000 to 1,500,000.

The reason for this is, when the number average molecular weight of suchan acrylic polymer becomes less than the value of 300,000, insufficiencyof the internal cohesive force of the adhesive agent may occur, andsometimes a part of adhesive is left behind. On the other hand, when thenumber average molecular weight of such an acrylic polymer exceeds thevalue of 1,500,000, uniform mixing may become difficult and the stableproperties may not be acquired.

Therefore, it is more preferable to set the number average molecularweight of this acrylic polymer at a value within the range of 500,000 to1,500,000, and it is even more preferable to set at a value within therange of 700,000 to 1,000,000.

The acrylic polymer's number average molecular weight can be measured byusing the Gel Permeation Chromatography (GPC) method.

(3) Glass Transition Temperature

Moreover, it is preferable to set the acrylic polymer's glass transitiontemperature (Tg1) at a value within the range of −70° C. to −10° C., andit is more preferable to set at a value within the range of −45° C. to−15° C.

The reason for this is when the acrylics polymer's glass transitiontemperature becomes less than −70° C., the medical pressure-sensitiveadhesive composition may be easily transferred to the back of substrate,or the skin stimulus may be increased. On the other hand, when theacrylic polymer's glass transition temperature exceeds −10° C., the peeladhesion strength to the skin of the medical pressure-sensitive adhesivecomposition may be remarkably lowered.

The glass transition temperatures of this acrylic polymer and an acrylicoligomer that will be mentioned later may either be measured by using aDifferential Scanning Calorimeter (DSC), or may also be calculated fromthe Fox formula.

(4) Aging Polymerization

Moreover, it is preferable that the acrylic polymer is subjected toaging polymerization through further addition of a polymerizationinitiator after the polymer is prepared by standard polymerization.

The reason for this is that the amount of remaining monomer in themedical pressure-sensitive adhesive composition may decrease remarkablyby adding an extra polymerization initiator after once the standardpolymerization is completed, so as to polymerize the remaining monomerefficiently. Therefore, skin stimulus that is caused by the remainingmonomer entering into the skin with the acrylic oligomer can beeffectively prevented.

So, it is preferable to set the second additional amount of thepolymerization initiator at a value within the range of 1 to 30 percentby weight relative to the first additional amount of the polymerizationinitiator.

2. Acrylic Oligomer

(1) Type

As a monomer component in the acrylic oligomer, a vinyl monomer, whichhas at least one lactam ring in the molecule, is used at content withinthe range of 10 to 40 percent by mole.

The reason for this is that by using the vinyl monomer, which has thelactam ring, the wetting area (S) against the skin is moderatelyincreased, and a predetermined peel adhesion strength (W=S×F) can easilybe obtained without increasing the adhesion strength (F) per unit areaspecific to an pressure-sensitive adhesive. Moreover, if the oligomercontained this vinyl monomer, even if comparatively large quantitieswere added, it would not cause the acrylic polymer's cohesive force tofall excessively. As a result an excellent peel property from the skincan be exhibited. Furthermore, if the oligomer contained this vinylmonomer, the compatibility with the acrylic polymer increased, and whena medicament and additive agents were added to the medicalpressure-sensitive adhesive composition, the medicaments and the likecould be dispersed easily.

As for a suitable example of the vinyl monomer with such a lactam ring,a water-soluble vinyl monomer can be mentioned, but especially, examplesthereof include N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone,N-vinyl-ε-caprolactam, and the like alone or combinations of at leasttwo thereof.

Moreover, the reason for setting the amount of the vinyl monomer with alactam ring at a value within the range of 10 to 40 percent by mole is,if the amount of the vinyl monomer with the lactam ring becomes at avalue below 10 percent by mole, the effect of increasing the wettingarea against the skin may not be exhibited. On the other hand, when theamount of the vinyl monomer with such a lactam ring exceeds 40 percentby mole, the plasticization of acrylic pressure-sensitive adhesivepolymer becomes inadequate, or its viscosity rises excessively, andthereby, uniform mixing with acrylic pressure-sensitive adhesive polymermay become difficult.

Therefore, it is more preferable to set the amount of the vinyl monomerwith a lactam ring at a value within the range of 12 to 35 percent bymole relative to the amount of the whole monomer components.

Moreover, although except for the vinyl monomer with a lactam ring, thetype of monomer component is not specifically limited. It is, however,preferable to use, for example, a (meth)acrylic acid alkyl ester withthe alkyl group's carbon number of 2 to 14. Specific examples include(meth)acrylic acid ethyl ester, (meth) acrylic acid propyl ester,(meth)acrylic acid isopropyl ester, (meth)acrylic acid 2-methoxyethylester, (meth)acrylic aced butyl ester, (meth)acrylic acid isobutylester, (meth)acrylic acid pentyl ester, (meth)acrylic acid hexyl ester,(meth)acrylic acid octyl ester, (meth)acrylic acid isooctyl ester,(meth)acrylic acid 2-ethylhexyl ester, (meth)acrylic acid nonyl ester,(meth)acrylic acid isononyl ester, and (meth)acrylic acid lauryl esteralone or combinations of at least two thereof. Furthermore, as for themonomer component of this acrylic oligomer, the combination of(meth)acrylic acid 2-ethylhexyl ester and N-vinyl-2-pyrrolidone ispreferable.

(2) Number Average Molecular Weight (Mn)

Moreover, it is preferable to set the number average molecular weight ofacrylic oligomer at a value within the range of 1,000 to 10,000.

The reason for this is, when the number average molecular weight of suchan acrylic oligomer becomes less than the value of 1,000, it becomeseasy to penetrate inside the skin and the skin stimulus property of themedical pressure-sensitive adhesive composition may increase. On theother hand, if the number average molecular weight of such an acrylicoligomer exceeds 10,000, the plasticization of the acrylic adhesiveagent polymer becomes inadequate, or the viscosity increasesexcessively, it becomes difficult to mix uniformly with the acrylicadhesive agent polymer, and furthermore, the wettability to the skin maybe reduced.

Therefore, it is even more preferable to set the number averagemolecular weight of this acrylic oligomer at a value within the range of1,200 to 7,000.

(3) Viscosity

Moreover, it is preferable to set the viscosity of the acrylic oligomer(measurement temperature: 25° C.) measured by a B type viscometer(Brookfield viscometer) at a value within the range of 10 to 1,000dPa·s.

The reason for this is, when the acrylic oligomer's viscosity becomesless than the value of 10 dPa·s, it becomes easy to penetrate inside theskin and sometimes this may cause skin stimulus to increase. On theother hand, when the acrylic oligomer's viscosity exceeds 1,000 dPa·s,the plasticization of the acrylic adhesive agent polymer may becomeinadequate, or the viscosity may be excessively increased, it becomesdifficult to mix uniformly with the acrylic adhesive agent polymer, andfurthermore, the wettability to the skin may be reduced.

Therefore it is more preferable to set the acrylic oligomer's viscosity(measurement temperature: 25° C.) at a value within the range of 15 to800 dPa·s, and it is even more preferable to set at a value within therange of 20 to 500 dPa·s.

(4) Additional Amount

Moreover, its distinctive feature is that the additional amount of theacrylic oligomer is within the range of 50 to 700 parts by weight,relative to 100 parts by weight of the acrylic polymer having across-linkable functional group. The reason for this is when theadditional amount of acrylic oligomer is less than the value of 50 partsby weight, the wettability to the skin may be remarkably reduced. On theother hand, when the additional amount of acrylic oligomer exceeds 700parts by weight, an excessive decrease in the cohesive force of theadhesive agent may occur, and a part of adhesive may be left on the skinor a predetermined peel adhesion strength may not be obtained.Therefore, it is more preferable to set the additional amount of theacrylic oligomer at a value within the range of 50 to 500 parts byweight relative to 100 parts by weight of the acrylic polymer having across-linkable functional group. In addition, as will be mentioned lateron, in the case an acrylic polymer having no cross-linkable functionalgroup is used together with the acrylic polymer having a cross-linkablefunctional group, it is more preferable to set the additional amount ofthe acrylic oligomer at a value within the range of 300 to 700 parts byweight relative to 100 parts by weight of the acrylic polymer having across-linkable functional group.

(5) Glass Transition Temperature

Moreover, it is preferable to set the glass transition temperature (Tg2)of an acrylic oligomer at a value within the range of −70° C. to −10° C.The reason for this is when the glass transition temperature of thisacrylic oligomer becomes a value below −70° C., the acrylic oligomer mayexude through, and the skin stimulus may increase. On the other hand,when the glass transition temperature of this acrylic oligomer exceeds−10° C., the wettability to the skin of the medical pressure-sensitiveadhesive composition may be reduced.

(6) Production Process

Moreover, although the producing process for an acrylic oligomer is notparticularly limited, it is preferable to carry out the polymerization(homopolymerization or copolymerization) of the acrylic monomer, whileadjusting the number average molecular weight, using a predeterminedamount of a chain transfer agent (Lauryl mercaptan, Mercaptoethanol,etc.), for example. To put it more specifically, it is preferable toproduce, for example, by solution polymerization in which a solvent,such as ethyl acetate, is used and a predetermined amount of the chaintransfer agent is added or by emulsion polymerization in which anaqueous solvent is used and a predetermined amount of the chain transferagent is added.

3. Acrylic Polymer having No Cross-Linkable Functional Group

(1) Type

It is preferable to use the acrylic polymer having no cross-linkablefunctional group together with the acrylic polymer having across-linkable functional group. That is, by using such acrylic polymersunitedly, the wettability against the skin can be improved withoutreducing cohesive force excessively.

Here, such an acrylic polymer having no cross-linkable functional groupis a polymer containing no vinyl monomer having a cross-linkablefunctional group as a monomer component, and is preferably an acrylicpolymer obtained by the polymerization of, for example, (meth)acrylicacid alkyl ester that has the alkyl group's carbon number of 1 to 14.More preferably, the acrylic polymer is obtained by the copolymerizationof the vinyl monomer with a lactam ring at within the range of, forexample, 1 to 40 percent by mole as in the acrylic oligomer.

(2) Number Average Molecular Weight (Mn) and Glass TransitionTemperature

The number average molecular weight and the glass transition temperatureof the acrylic polymer having no cross-linkable functional group are thesame as that described above with respect to the acrylic polymer havinga cross-linkable functional group.

(3) Additional Amount

In the case where the acrylic polymer having no cross-linkablefunctional group is used together with the acrylic polymer having across-linkable functional group, it is preferable to set the additionalamount at a value within the range of 1 to 50 percent by weight relativeto the whole amount of the medical pressure-sensitive adhesivecomposition. The reason for this is when this additional amount becomesless than the value of 1 percent by weight, the effect of the additionmay not appear and the wettability against the skin may not improve. Onthe other hand, when the additional amount exceeds 50 percent by weight,the existence amount of the acrylic polymer having a cross-linkablefunctional group is decreased relatively, and as a result, the cohesiveforce may be reduced. Therefore, it is more preferable to set theadditional amount of the acrylic polymer having no cross-linkablefunctional group at a value within the range of 5 to 40 percent byweight against the whole amount of the medical pressure-sensitiveadhesive composition, and it is even more preferable to set at a valuewithin the range of 10 to 35 percent by weight.

4. Cross-Linking Agent

Moreover, it is preferable to cross-link by adding a cross-linking agentinto the intermediate composition that includes an acrylic polymer andan acrylic oligomer. That is, for example, it is preferable to add thecross-linking agent of 0.01 to 15 percent by weight relative to theamount of the whole intermediate composition, in order to adjust thecohesive force of the acrylic polymer. The reason for this is when theadditional amount of such a cross-linking agent becomes less than thevalue of 0.01 percent by weight, a part of adhesive may be left behindbecause of inadequacy of the cross-linking. On the other hand, when theadditional amount of such a cross-linking agent exceeds 15 percent byweight, the wettability to the skin may be remarkably reduced because ofexcessive cross-linking. Therefore, it is more preferable to set theadditional amount of such a cross-linking agent at a value within therange of 0.05 to 8 percent by weight relative to the amount of the wholeintermediate composition, and it is even more preferable to set at avalue within the range of 0.1 to 5 percent by weight. In addition, aspreferable sorts of cross-linking agent, for example, polyvalent epoxycompounds, such as ethylene glycol-diglycidyl ether and triglycidylisocyanurate, polyvalent isocyanate compounds as addition derivatives oftolylene diisocyanate or hexamethylene diisocyanate, polyvalentaziridine compounds, polyvalent metal chelate compounds, and the likecan be listed.

5. Additive Agent

(1) Medicament

Moreover, a medicament can be added as an additive agent so that apredetermined effect of the medicament can work in the medicalpressure-sensitive adhesive composition. The type of medicament is notparticularly limited, and example thereof may include anti-inflammatoryagent, anti-inflammatory anodyne, coronary vasodilators, asthma,antihypertensive agent, anti-histaminic, tranquilizer, anti-biotic,anesthetic, vitamin preparation, and the like alone or combinations ofat least two thereof. Moreover, although the additional amount of themedicament varies depending on the type of medicament, or the usage ofthe medical pressure-sensitive adhesive composition, and for example, itis preferable to set it at a value within the range of 0.1 to 30 percentby weight relative to the amount of the whole medical pressure-sensitiveadhesive composition.

(2) Other Additive Agents

Moreover, it is preferable to add various additive agents in the medicalpressure-sensitive adhesive composition. Examples thereof include ananti-oxidant, a viscosity control agent, a UV absorber, a hiding agent,a plasticizer, wax, a coloring agent, an inorganic filler, an organicfiler, an expander, a coupling agent and the like alone or combinationsof at least two thereof.

6. Corneous Picking Area Ratio

Moreover, in the peeling test with respect to the skin as shown inexample 1, it is preferable to set the corneous picking area ratio at avalue of less than 30percent. The reason for this is when such acorneous picking area ratio exceeds 30 percent, the skin stimulusbecomes excessively high, and this may cause discomfort at the time ofuse or may excessively lower the re-adhesion property. However, if thecorneous picking area ratio becomes excessively small, the type ofacrylic monomer that can be used for the acrylic oligomer or the acrylicpolymer may be restricted excessively. Therefore, it is more preferableto set the corneous picking area ratio at a value within the range of0.1 to 20 percent and it is even more preferable to set the value withinthe range of 0.5 to 5 percent.

7. Waterdrop Contact Angle

Moreover, as for the detailed waterdrop contact angle shown in example1, it is preferable to set this water drop contact angle at a valuewithin a range of 10° to 70°. The reason for this is when the waterdropcontact angle is decreased to the value of less than 10°, skin stimulusmay become excessively high and this may cause discomfort at the time ofuse. On the other hand, if this waterdrop contact angle exceeds 70°, thetype of acrylic monomer that can be used for the acrylic oligomer or theacrylic polymer may be excessively restricted. Therefore, it is morepreferable to set the waterdrop contact angle at a value within therange of 12° to 50°, it is even more preferable to set at a value withinthe range of 15° to 40°.

8. Production Process

Moreover, although the production process for the medicalpressure-sensitive adhesive composition is not particularly limited, itis preferable to refer to the following production steps (1) to (4), forexample. When it is carried out like this, the mixing and dispersion ofthe acrylic polymer and the acrylic oligomer become more easily, and themedical pressure-sensitive adhesive composition having an excellentre-adhesion property can be obtained efficiently.

-   (1) a step to prepare the acrylic polymer that has a number average    molecular weight of 300,000 to 1,500,000 and has cross-linkable    functional groups-   (2) a step to prepare the acrylic oligomer that has a number average    molecular weight of 1,000 to 10,000 produced by polymerization of    monomer components containing 10 to 40 percent by mole of vinyl    monomer with a lactam ring-   (3) a step to prepare an intermediate composition by compounding an    acrylic oligomer within the range of 50 to 700 parts by weight    relative to 100 parts by weight of the acrylic polymer-   (4) a step to cross-link the intermediate composition by adding the    cross-linking agent

In addition, it is also preferable that the acrylic polymer having nocross-linkable functional group is prepared by polymerization in advanceand if required, the step of adding and mixing the resultant polymer tothe intermediate composition is carried out or the step of furtheradding and mixing the medicament and the additive agent is carried out.

[Second Embodiment]

As illustrated in FIG. 1(a), the second embodiment is a medical tape 10in which a medical pressure-sensitive adhesive composition 12 islaminated on a substrate 14, wherein the medical pressure-sensitiveadhesive composition is prepared by cross-linking an intermediatecomposition containing an acrylic polymer having a cross-linkablefunctional group and an acrylic oligomer prepared by polymerization ofmonomers containing at least a vinyl monomer with a lactam ring throughthe use of a cross-linking agent ,and the medical pressure-sensitiveadhesive composition is obtained by incorporating 100 parts by weight ofthe acrylics polymer having the number average molecular weight at avalue within the range of 300,000 to 1,500,000, and 50 to 700 parts byweight of the acrylics oligomer having the number average molecularweight at a value within the range of 1,000 to 10,000.

1. Substrate

(1) Type

The type of substrate is not particularly limited, and examples thereofinclude a polyurethane film, a polyester film, a polyvinyl chloridefilm, a polyolefin film, a polycarbonate film, a polysulfone film, apolyphenylene sulfide film, a polyimide film, a paper, a film containingglass fiber, and the like.

In addition, the form of the substrate is not particularly limited aswell; and for example, mesh-type or even fabrics or nonwoven fabrics arefavorable.

(2) Thickness

Moreover, it is preferable to set the thickness of the substrate shownin FIGS. 1(a) to (c) at a value within the range of 5 to 2,000 μm. Thereason for this is when the thickness of such a substrate is less invalue than 5 μm, the mechanical strength is reduced and it may not besuitable for the use in the medical adhesive tape. On the other hand,when the thickness of this substrate exceeds 2,000 μm, the handlingbecomes difficult because of the excessive thickness, and also when themedical adhesive tape is made, it may easily peel off the skin and thelike. Therefore, it is more preferable to set the thickness of thesubstrate at a value within the range of 10 to 1,000 μm, and it is evenmore preferable to set at a value within the range of 20 to 500 μm.

(3) Primer Layer

As shown in FIG. 1(b), it is preferable to form a primer layer 16(including a sizing layer) on the surface of the substrate 14. Byconstituting like this, the adhesion strength between the substrate 14and the adhesive agent layer 12, which consists of a medicalpressure-sensitive adhesive composition can be increased, and thetransfer of the medical pressure-sensitive adhesive composition to thebackside of the substrate can be effectively prevented. In addition, asfor such a primer layer, it is preferable to constitute from an acrylicresin, an epoxy resin and the like.

(4) Releasing Layer

As shown in FIG. 1(c), it is preferable to form a releasing layer 18 onthe surface of the substrate 14 opposite to the side where the medicalpressure-sensitive adhesive composition is formed. By constituting likethis, not only rolling out from the roll type medical adhesive tapebecomes easy, but also the transfer of the medical pressure-sensitiveadhesive composition to the backside of the substrate can be preventedeffectively. In addition, it is preferable to constitute such areleasing layer treated with a silicone resin or a long-chain alkylcompound, for example.

2. Medical Pressure-Sensitive Adhesive Composition

Since the same medical pressure-sensitive adhesive composition asdescribed in the first embodiment can be used here, the explanationthereof will not be provided.

3. Production Process

Although the production process for the medical tape is not limited, thetape can be produced easily by uniformly applying the medicalpressure-sensitive adhesive composition to the substrate, by using aroll coater, a comma coater, a knife coater, and such, for example.

4. Peel Adhesion Strength

Moreover, it is preferable to set the peel adhesion strength (mode: 180°peel-off, substrate: phenolic resin plate, peeling speed: 300 mm/min) ofthe medical tape having the adhesive layer that consists of an medicalpressure-sensitive adhesive composition in accordance with JIS Z0237 atthe value within the range of 50 to 250 cN/12 mm. The reason for this iswhen such peel adhesion strength is less than 50 cN/12 mm, the tape maypeel-off too easily from the skin and the function as a medical adhesivetape may become poor.

On the other hand, if this peel adhesion strength exceeds 250 cN/12 mm,it may become difficult to remove the medical pressure-sensitiveadhesive composition from the skin and skin stimulus may becomeexcessive and cause discomfort during use. Therefore, it is morepreferable to set at a value within the range of 60 to 200 cN/12 mm, andit is even more preferable to set at a value within the range of 80 to150 cN/12 mm. In addition, it is also preferable to adjust the peeladhesion strength of the medical tape by applying the medicalpressure-sensitive adhesive composition with a pattern coating methodinstead of applying it all over the substrate surface.

EXAMPLES

The examples of the present invention are explained in detail hereafter.However, needles to say, the following explanation only exemplifies thepresent invention and the scope of the present invention should not belimited by these descriptions in anymore.

Example 1

1. Production Process for Medical Pressure-Sensitive AdhesiveComposition and Medical Tape

(1) Preparation of an Acrylic Oligomer

A monomer mixture solution was prepared by uniformly dissolving 20.5 g(0.185 mol, mixture mole fraction: 12 percent by mole) ofN-vinyl-2-pyrrolidone, 250 g (1.356 mol, mixture mole fraction: 88percent by mole) of acrylic acid 2-ethylhexyl ester, and 18.2 g (0.09mol) of Lauryl mercaptan as a chain transfer agent into 73 g of ethylacetate as a solvent. 0.5 g of azobisisobutyronitrile (AIBN) was addedas a polymerization initiator after laying this monomer mixed solutionin a polymerization reactor equipped with an agitator and a vaporcondensation reflux tower. Subsequently, after agitating was furtherperformed until the monomer mixed solution becomes homogeneous, thepolymerization reactor was immersed in a hot water bath at 60° C., andsolution polymerization was started. The polymerization reaction wascontinued for about 6 hours, while controlling the temperature ofpolymerization reactive solution at 65° C.±5° C. Subsequently,polymerization reaction solution was taken out from the polymerizationreactor, and when the concentration (nonvolatile content) of theobtained acrylic oligomer was measured by the dry weight method (150°C., 1 hour), it was 80.4 percent by weight. Moreover, the obtainedpolymerization reaction solution was heated to 85° C. underdecompression of 1 mmHg, the ethyl acetate serving as a solvent wasremoved, and the viscous acrylic oligomer was obtained. When theviscosity of the obtained acrylic oligomer was measured by using a Btype viscometer, it was 65 dPa·s(measurement temperature: 25° C., thesame holds true in the following description), and the number averagemolecular weight measured by using the GPC method (the same holds truein the following description) was 3,200.

(2) Preparation of Acrylic Polymer having a Cross-Linkable FunctionalGroup

A monomer mixed solution was prepared by dissolving 10 g (5.5 parts byweight) of acrylic acid and 180 g (100 parts by weight) of acrylic acid2-ethylhexyl ester into 232 g of ethyl acetate. Subsequently, theobtained monomer mixed solution was put into the polymerization reactorequipped with a vapor condensation reflux tower and an agitator, afteradding 0.14 g of AIBN as a polymerization initiator, immersion into ahot water bath at 58° C., and the solution polymerization was started.The solution polymerization was continued for about 3 hours, whilecontrolling the temperature of the polymerization solution at 65° C.±5°C. In addition, at the stage where an exothermic reaction had mostlyended, the temperature was raised up to 70° C.±2° C. after 0.04 g ofAIBN was added again, the heating procedure was continued for about 5hours, so that the polymerization reaction was completed. Subsequently,the polymerization reaction solution was taken out of the polymerizationreactor and the concentration (nonvolatile content) of the obtainedacrylic polymer was measured by the dry weight method (150° C., 1 hour),and the result was 45.5 percent by weight. Moreover, the solutionviscosity of the obtained acrylic polymer (viscosity of an ethyl acetatesolution measured by using a B type viscometer, the same holds true inthe following description) was measured, and the result was 35 dPa·s.The number average molecular weight, which was measured by the GPCmethod, was 750,000.

(3) Cross-Linking and Lamination Step

An intermediate composition was prepared by mixing 85 g of the resultantacrylic oligomer and 100 g (45.5 g in terms of acrylic polymer) of theacrylic polymer in an ethyl acetate solution. 3 g of polyvalentisocyanate compound (Nippon Polyurethane Industry Co. Ltd., Coronate-HL)serving as a reactive cross-linking agent was added into theintermediate composition. Afterwards, ethyl acetate was further addedfor concentration adjustment, and the medical pressure-sensitiveadhesive composition (ethyl acetate solution) which had a nonvolatileresidue content of 50 percent by weight, was obtained. The content ofthe acrylic oligomer in this medical pressure-sensitive adhesivecomposition was 65 percent by weight. Subsequently, after the medicalpressure-sensitive adhesive composition was uniformly laminated on thepolyester nonwoven fabric (200 μm in thickness) treated by sizingprocess to prevent the permeability to the backside, drying procedurewas carried out by heating at 110° C., so that a medical tape (adhesiveplaster) with an adhesion layer having a thickness of 40 μm wasprepared.

2. Evaluation

(1) Peel Adhesion Strength

The peel adhesion strength of the obtained medical tape was measured inaccordance with JIS Z0237. The obtained result is shown in Table 1.

(2) Corneous Picking Area Ratio

The obtained medical tape was cut into strip specimens (width: 12 mm,length: 40 mm, effective adhesion area: 480 mm 2), and the resultantspecimens were applied to the five-evaluator's inner skin of the upperarm. Afterwards, the specimens were peeled off after being applied for24 hours respectively. Subsequently, the surface of the adhesion layerof the peeled medical tape was dyed with a dye solution (Gentian Violetand Brilliant Green), and the corneous layer that adhered to the surfaceof the adhesion layer by the peeling failure became dark purple color.By the image analysis method through the microphotograph, the coloringarea ratio of the corneous layer (total of the area which was colored indark purple/adhesion layer area×100) was measured as a corneous pickingarea ratio. The obtained result is shown in Table 1.

(3) Re-Adhesion Property

The obtained medical tape was cut into strip specimens (width: 12 mm,length: 100 mm, effective adhesion area: 1,200 mm²), and the specimenwas applied to a person's skin on the upper back. Then, peel adhesionstrength was measured as shown in the above (1) after the specimen washeld intact for 20 minutes and was peeled off. This operation wasrepeated 5 times in total, and the re-adhesion property was evaluated.The obtained result is shown in Table 2.

In addition, with regard to the re-adhesion property, a relation betweenthe frequency of the skin pasting/peeling and the maintenance ratio ofpeel adhesion strength (percent) are shown in FIG. 2 based on the resultshown in Table 2. If the value of the peel adhesion strength(maintenance ratio of peel adhesion strength) is at least 50 percent ofthe initial peel adhesion strength after repeating at least five times,the practicality is excellent. Furthermore, if the value is 80 percentor more, it can be adhered practically many more times and this provesthe outstanding practicality.

(4) Waterdrop Contact Angle

The waterdrop contact angle (measurement temperature: 25° C.) in theadhesion layer surface of the obtained medical tape was measured byusing a contact angle measurement apparatus (made by MasudaCorporation). The obtained result is shown in Table 1.

(5) Unstuck Tendency, Skin Stimulus Tendency, and Adhesive Left Tendency

The obtained medical tape was processed into strip specimens (width: 12mm, length: 40 mm, effective adhesion area: 480 mm²). After pasting thespecimens to the inner skin of the upper arm of the five evaluators for24 hours, the tendencies for unstuck, skin stimulus, and adhesive leftwere evaluated based on the following standards, respectively. Theobtained result is shown in Table 1.

(Unstuck Tendency)

-   Very good: All of the five people did not experience the specimen    coming unstuck.-   Good: Four or more people did not experience the specimen coming    unstuck.-   Fair: Three or more people did not experience the specimen coming    unstuck.-   Bad: Three or more people experienced the specimen coming unstuck.

(Skin Stimulus Tendency)

-   Very good: There was no skin stimulus at all according to the    average experience of the five people.-   Good: There was almost no skin stimulus according to the average    experience of the five people.-   Fair: There was slight skin stimulus according to the average    experience of the five people.-   Bad: There was notable skin stimulus according to the average    experience of the five people.

(Adhesive Left Tendency)

-   Very good: There was no adhesive left according to the average    experience of the five people.-   Good: There was almost no adhesive left behind according to the    average experience of the five people.-   Fair: There was slight adhesive left according to the average    experience of the five people.-   Bad: There was remarkable adhesive left according to the average    experience of the five people.

Examples 2 to 4

As shown in Table 1, the medical tape was made and evaluated like theexample 1, except to change the monomer composition and the additionalamount within the limits of the present invention. Consequently, ineach, while proper peel adhesion strength to the skin is shown, thecorneous picking area ratio is at a very low value. And at the sametime, it becomes clear that it is possible to have a medical tape thathas excellent re-adhesion property. TABLE 1 Example 1 Example 2 Example3 Example 4 Acrylic Charge (g) 2EHA 250 250 250 170 Oligomer A NVP 20.581.9 20.5 99 2MEA — — — 150 LM 18.2 67.1 9.1 42.4 Viscosity (dPa · Sec)65 21 320 125 Number Average Molecular Weight 3200 1200 6200 2200 MolarFraction of NVP (%) 12.0 35.2 12.0 30.1 Glass TransitionTemperature(Tg2, ° C.) −41.5 −18.6 −41.0 −20.2 Crosslinkable Charge (g)2EHA 180 180 180 375 acrylic MMA — — — 125 polymer B AA 10 10 10 25Number Average Molecular Weight 750000 750000 750000 910000 GlassTransition Temperature(Tg1, ° C.) −45.3 −45.3 −45.3 −20.6 PSA AdditionalAcrylic Oligomer A 85.0 45.5 45.5 16.4 amount (g) Crosslinkable AcrylicPolymer B 45.5 45.5 45.5 30.4 Reactive Crosslinking Agent 3.0 2.0 1.81.6 Weight Ratio A/B × 100 187 100 100 54 Evaluation Peel AdhesionStrength (cN/12 mm) 101 88 107 118 Corneous sticking area ratio(%) 0.70.9 1.8 3.2 Waterdrop Contact Angle (°) 41 22 44 28 Unstuck TendencyVery good Very good Very good Very good Paste left Tendency Very goodVery good Very good Very good Skin Stimulus Tendency Very good Very goodVery good Very good2EHA: Acrylic acid 2-ethylhexyl esterNVP: N-vinyl-2-pyrrolidone2MEA: Acrylic acid 2-methoxyethyl esterLM: Lauryl mercaptanMMA: Methacrylic acid methyl esterAA: Acrylic acid

TABLE 2 Peel Adhesion Strength The frequency of the skin pasting (cN/12mm) 0 time 1 time 2 times 3 times 4 times 5 times Example 1 102 100 9998 95 93 Example 5 108 103 98 96 95 90 Comp. 255 30  0 — — — Example 9Comp. 146 90 65 48 42 32 Example 10 Comp. 150 112 82 69 58 46 Example 11

Example 5

1. Production Process for the Medical Pressure-Sensitive AdhesiveComposition and the Medical Tape

(1) Preparation of an Acrylic Oligomer

Based on example 1, an acrylic oligomer liquid was obtained by acombination as shown in table 3. The viscosity of the obtained acrylicoligomer was 390 dPa·s, and the number average molecular weight was3,200.

(2) Preparation of the Acrylic Polymer having a Cross-LinkableFunctional Group

A monomer mixed solution was prepared by dissolving 20 g (11 parts byweight) of acrylic acid and 180 g (100 parts by weight) of acrylic acid2-ethylhexyl ester into 300 g of ethyl acetate. Subsequently, theobtained monomer mixed solution was put in the polymerization reactorequipped with a vapor condensation reflux tower and an agitator, andafter 0.15 g of AIBN as a polymerization initiator, immersion into a hotwater bath at 58° C. was performed, and the solution polymerization wasstarted. The solution polymerization was continued for about 3 hours,while controlling the temperature of the polymerization liquid at 65°C.±5° C. In addition, at the stage where an exothermic reaction hadmostly ended, the temperature was raised up to 70° C.±2° C. after 0.04 gof AIBN was added again, the heating procedure was continued for about 5hours, so that the polymerization reaction was completed. Subsequently,the polymerization reaction solution was taken out of the polymerizationreactor and the concentration (nonvolatile content) of the obtainedacrylic polymer was measured by the dry weight method (150° C., 1 hour),and the result was 40.7 percent by weight. Moreover, the solutionviscosity of the obtained acrylic polymer was 55 dPa·s, and the numberaverage molecular weight was 820,000.

(3) Preparation of the Acrylic Polymer having No Cross-LinkableFunctional Group

A monomer mixture solution was formed by dissolving 36.7 g ofN-vinyl-2-pyrrolidone and 140 g of acrylic acid 2-ethylhexyl ester into265 g of ethyl acetate. Subsequently, the obtained monomer mixedsolution was put in the polymerization reactor equipped with a vaporcondensation reflux tower and angitator, after adding 0.13 g of AIBN asa polymerization initiator, immersion into a hot water bath at 58° C.,and the solution polymerization was started. The solution polymerizationwas continued for about 3 hours, while controlling the temperature ofthe polymerization liquid at 65° C.±5° C. In addition, at the stagewhere an exothermic reaction had mostly ended, the temperature wasraised up to 70° C.±2° C. after 0.035 g of AIBN was added again, theheating procedure was continued for about 5 hours, so that thepolymerization reaction was completed. Subsequently, the polymerizationreaction solution was taken out of the polymerization reactor and theconcentration of the obtained acrylic polymer was measured by the dryweight method, and the result was 41 percent by weight. Moreover, thesolution viscosity of the obtained acrylic polymer was 360 dPa·s, andthe number average molecular weight was 880,000.

(4) The Cross-Linking and Laminating Process

An intermediate composition was prepared by mixing 60 g of the resultantacrylic oligomer, 23 g (9 g in terms of acrylic polymer) of an acrylicpolymer solution having a cross-linkable functional group, and 48 g (20g in terms of acrylic polymer) of an acrylic polymer solution having nocross-linkable functional group. 0.9 g of polyvalent isocyanate compoundwas added as a reactive cross-linking agent (manufactured by NipponPolyurethane Industry Co. Ltd., Coronate-HL) to the intermediatecomposition. Afterwards, ethyl acetate was further added for adjustment,and the medical pressure-sensitive adhesive composition (ethyl acetatesolution) which had a nonvolatile residue content of 50 percent byweight, was obtained. The content of the acrylic oligomer in thismedical pressure-sensitive adhesive composition was 67 percent byweight. Subsequently, after the medical pressure-sensitive adhesivecomposition was uniformly laminated on the polyester nonwoven fabric(200 μm in thickness) that had been treated by sizing process to preventthe permeation to the backside, drying procedure was carried out byheating at 110° C., so that a medical tape (adhesive plaster) with anadhesion layer having a thickness of 40 μm was prepared.

2. Evaluation

With regard to the peel adhesion strength of the obtained medical tapeand the corneous picking area ratio and the like, are estimated in thesame way as in example 1. Consequently, as shown in Table 3 and in apart of FIG. 2, in each, while proper peel adhesion strength to the skinis shown, it becomes clear that it is possible to provide a medical tapewhich has very fine re-adhesion property (maintenance ratio of peeladhesion strength). TABLE 3 Example 5 Example 6 Acrylic Oligomer ACharge (g) 2EHA 250 250 NVP 64.6 64.6 LM 21.2 21.2 Viscosity(dPa · Sec)390 390 Number Average Molecular Weight 3200 3200 Molar Fraction of NVP(%) 30.0 30.0 Glass Transition Temperature (Tg2, ° C.) −24.6 −24.6Crosslinkable Charge (g) 2EHA 180 180 acrylicpolymer B AA 20 20 NumberAverage Molecular Weight 820000 820000 Glass Transition Temperature(Tg1,° C.) −45 −45 Non-cross linkable Charge (g) 2EHA 140 140 acrylic polymerC NVP 36.7 42.1 Number Average Molecular Weight 880000 840000 GlassTransition Temperature(Tg3, ° C.) −19.4 −17.6 PSA Additional AcrylicOligomer A 60.0 40.0 amount (g) Crosslincable Acrylic Polymer B 9 10Non-cross lincable Acrylic 20 20 Polymer C Reactive Cross linking Agent0.9 0.9 Weight Ratio A/B × 100 667 400 Evaluation Peel Adhesion Strength(cN/12 mm) 105 95 Corneous sticking area ratio (%) 0.8 1.1 WaterdropContact Angle (°) 18 33 Unstuck Tendency Very good Very good Paste leftTendency Very good Very good Skin Stimulus Tendency Very good Very good2EHA: Acrylic acid 2-ethylhexyl esterNVP: N-vinyl-2-pyrrolidoneLM: Lauryl mercaptanAA: Acrylic acid

Example 6

As shown in Table 3, within the limits of the present invention, exceptfor changing the additional amount of the acrylic polymer having nocross-linkable functional group, the medical pressure-sensitive adhesivecomposition and the medical tape was created and evaluated in the sameway as in example 5.

[Comparative Examples 1 to 11]

As shown in Table 4 and in a part of FIG. 2, in comparative examples 1to 11, except for changing the monomer composition and the additionalamount outside the limits of the present invention respectively, themedical tape was created and evaluated based on example 1.

Consequently, in comparative example 1, the cohesive failure of theadhesive agent was intense due to not adding the cross-linking agent, sothat an evaluation test was unable to be carried out.

Also, in comparative example 2, since the number average molecularweight of the acrylic polymer having a cross-linkable functional groupis too little, it becomes clear that the value of corneous picking arearatio is extremely high, and the peeling damage on the skin (corneouslayer) is very large, for example.

Also, in comparative example 3, since the numeric average molecularweight of the acrylic oligomer is too little, it becomes clear thatserious skin stimulus and notable itching occur, for example.

Also, in comparative example 4, since the number average molecularweight of the acrylic oligomer is too much, it becomes clear that, as anexample, the value of corneous picking area ratio is high, and thepeeling damage to the skin (corneous layer) is greater.

Also, in comparative example 5, due to the very small additional amountof acrylic oligomer, it becomes clear that, as an example, the value ofcorneous picking area ratio is high, and the peeling damage to the skin(corneous layer) is therefore greater.

Also, in comparative example 6, due to a greater additional amount ofacrylic oligomer, cohesive failure of the adhesive agent was intense andan evaluation test was unable to be carried out.

Also, in comparative example 7, since the molar fraction ofN-vinyl-2-pyrrolidone in an acrylic oligomer is too small, it becomesclear that the value of corneous picking area ratio is high, and thenthe peeling damage to the skin (corneous layer) is large as well, forexample.

Also, in comparative example 8, since the molar fraction ofN-vinyl-2-pyrrolidone in an acrylic oligomer is too high, it becomesclear that the value of corneous picking area ratio is high, and thepeeling damage to the skin (corneous layer) is large as well, forexample.

Also, in comparative example 9, due to no addition of the acrylicoligomer, it becomes clear that, as an example, the value of corneouspicking area ratio is extremely high, and the re-adhesion property ispoor, as shown in Table 2 and FIG. 2.

Also, in comparative example 10, due to not using a vinyl monomer havinga lactam ring at all, for an acrylic oligomer it becomes clear, as anexample, that the value of corneous picking area ratio is high, and there-adhesion property is poor, as shown in Table 2 and FIG. 2.

Moreover, in comparative example 11, although the plasticizer is added,due to not adding the specific acrylic oligomer at all, it becomesclear, as an example, that the value of corneous picking area ratio ishigh, and the re-adhesion property is poor, as shown in Table 2 and FIG.2. TABLE 4 Comp. Ex. 1 Comp. Ex. 2 Comp. Ex. 3 Comp. Ex. 4 Comp. Ex. 5Comp. Ex. 6 Acrylics Charge (g) 2EHA 250 250 250 250 250 250 oligomer orNVP 20.5 20.5 81.9 20.5 81.9 20.5 liquid LM 18.2 18.2 134 3.6 67.1 18.2material A Viscosity(dPa * Sec) 65 65 4 N.A. 21 65 Number AverageMolecular Weight 3200 3200 700 15000 1200 3200 Molar Fraction of NVP (%)12.0 12.0 35.2 12.0 35.2 12.0 Glass Transition Temperature(Tg2, ° C.)−41.5 −41.5 −18.6 −41.0 −18.6 −41.5 Cross Charge (g) 2EHA 180 180 180180 180 180 linkable AA 10 10 10 10 10 10 acrylic Number AverageMolecular Weight 750000 100000 750000 750000 750000 750000 polimer BGlass Transition Temperature(Tg1, ° C.) −45.3 −45.6 −45.3 −45.3 −45.3−45.3 PSA Additional Acrylic Oligomer A 45.0 45.5 22.8 45.5 11.0 80.0amount (g) Liquid Material — — — — — — Cross linkable acrylic polimer B45.5 45.5 45.5 45.5 45.5 10.0 Reaction Type Cross linking none 2.0 1.51.8 1.6 1.2 Agent Weight Ratio A/B × 100 100 100 50 100 24 800Evaluation Waterdrop Contact Angle (*) 35 39 31 47 75 36 Peel AdhesionStrength (cN/12 mm) * 265 120 184 192 * Unstuck Tendency Very good Verygood Very good Very good Paste left Tendency Fair Very good Very goodVery good Skin Stimulus Tendency Bad Bad Bad Bad Corneous sticking arearatio (%) 74 4.5 33 38 Comp. Ex. 7 Comp. Ex. 8 Comp. Ex. 9 Comp. Ex. 10Comp. Ex. 11 Acrylics Charge (g) 2EHA 250 250 — 250 MIP oligomer or NVP7.1 127 — — liquid LM 26.0 76.0 — 25.3 material A Viscosity(dPa * Sec)10 N.A — 3.9 0.1 or less Number Average Molecular Weight 2200 1200 —2200 271 Molar Fraction of NVP (%) 4.5 45.7 — — — Glass TransitionTemperature(Tg2, ° C.) −47.0 −4.8 — −50.2 — Cross Charge (g) 2EHA 180180 180 180 180 linkable AA 10 10 10 10 10 acrylic Number AverageMolecular Weight 750000 750000 750000 750000 750000 polimer B GlassTransition Temperature(Tg1, ° C.) −45.3 −45.3 −45.3 −45.3 −45.3 PSAAdditional Acrylic Oligomer A 45.5 45.5 — 45.5 — amount (g) LiquidMaterial — — — — 45.5 Cross linkable acrylic polimer B 45.5 45.5 45.545.5 45.5 Reaction Type Cross linking 1.2 1.2 0.4 1.4 2.0 Agent WeightRatio A/B × 100 100 100 0 100 100 Evaluation Waterdrop Contact Angle (*)104 12 115 124 121 Peel Adhesion Strength (cN/12 mm) 166 174 253 150 147Unstuck Tendency Very good Very good Very good Very good Very good Pasteleft Tendency Very good Very good Very good Very good Very good SkinStimulus Tendency Bad Fair Bad Fair Fair Corneous sticking area ratio(%) 31 29 89 22 242EHA: Acrylic acid 2-ethylhexyl esterNVP: N-vinyl-2-pyrrolidoneLM: Lauryl mercaptanMIP: Myristicacid isopropylAA: Acrylic acid*Since cohesive failure of an adhesive agent was intense, an evaluationtest could not be carried out.Industrial Applicability

According to the present invention, the intermediate composition isprepared earlier on, and the intermediate composition is prepared byadding a predetermined amount of specific type of acrylic oligomerhaving a predetermined number average molecular weight (Mn) to theacrylic polymer which has cross-linkable functional groups and whichalso has a predetermined number average molecular weight (Mn). Bycrosslinking the intermediate composition, a medical pressure-sensitiveadhesive composition and a medical tape that cause only low skinstimulus while having an excellent re-adhesion property can be preparedwherein the wettability against the skin is kept high and appropriatepeel adhesion strength is maintained. Therefore, a suitable medical tapeis provided, which can be repeatedly adhered in postoperative treatment,artificial dialysis therapy, and the like. Moreover, according to thepresent invention, there is an excellent compatibility between theacrylic polymer and acrylics oligomer, but because the acrylic oligomeris locked up in the cross-linked acrylic polymer, even though themedical tape is rolled up in a roll shape and saved under hightemperature condition or saved for a long time, the leak out of acrylicoligomer is decreased, and the transfer to the substrate back can beeffectively prevented. Therefore, a product that is suitable as amedical tape having significant easiness in both manufacturing andstorage.

1. A medical pressure-sensitive adhesive composition, in which anintermediate composition is cross-linked through the use of across-linking agent, wherein the intermediate composition contains anacrylic polymer having a cross-linkable functional group and an acrylicoligomer prepared by polymerization of monomers containing 10 to 40percent by weight of vinyl monomer with a lactam ring, while the numberaverage molecular weight of the acrylic polymer is set at a value withinthe range of 300,000 to 1,500,000, the number average molecular weightof the acrylic oligomer is set at a value within the range of 1,000 to10,000, and the medical pressure-sensitive adhesive composition is madeby compounding the acrylic oligomer in the range of 50 to 700 parts byweight relative to 100 parts by weight of acrylic polymer.
 2. Themedical pressure-sensitive adhesive composition according to claim 1,wherein an acrylic polymer having no cross-linkable functional group isincluded other than the acrylic polymer having a cross-linkablefunctional group, and the additional amount of this acrylic polymer isset at a value within the range of 1 to 50 percent by weight, relativeto the whole amount of the medical pressure-sensitive adhesivecomposition.
 3. The medical pressure-sensitive adhesive compositionaccording to claim 1, wherein the acrylic oligomer contains a(meth)acrylic acid alkyl ester monomer as a monomer component, and themolar fraction of this (meth)acrylic acid alkyl ester monomer is set ata value within the range of 60 to 90 percent by mole relative to thewhole amount of the oligomer.
 4. The medical pressure-sensitive adhesivecomposition according to claim 1, wherein the acrylic oligomer includes2-ethylhexylacrylic ester and N-vinyl-2-pyrrolidone as monomercomponents.
 5. The medical pressure-sensitive adhesive compositionaccording to claim 1, wherein the viscosity (25° C.) of the acrylicoligomer is set at a value within the range of 10 to 1,000 dPa·s.
 6. Themedical pressure-sensitive adhesive composition according claim 1,wherein a medicament is included at content within the range of 0.1 to30 percent by weight relative to the whole amount of medicalpressure-sensitive adhesive composition.
 7. A process for producing amedical pressure-sensitive adhesive composition including the followingsteps (1) to (4); (1) a step for preparing an acrylic polymer that has anumber average molecular weight of 300,000 to 1,500,000 and hascross-linkable functional groups (2) a step for preparing an acrylicoligomer that contains 10 to 40 percent by mole of vinyl monomer with alactam ring as a monomer component (3) a step for preparing anintermediate composition by compounding an acrylic oligomer within therange of 50 to 700 parts by weight relative to 100 parts by weight ofacrylic polymer and (4) a step for adding a cross-linking agent into theintermediate composition obtained from the step (3) so as to carry outthe cross-linking
 8. A medical tape, in which a medicalpressure-sensitive adhesive composition is laminated on a substrate,wherein the medical pressure-sensitive adhesive composition is preparedby cross-linking an intermediate composition containing an acrylicpolymer having a cross-linkable functional group and an acrylic oligomerprepared by polymerization of monomers containing 10 to 40 percent bymole of vinyl monomer with a lactam ring through the use of across-linking agent, and wherein this medical tape is made bycompounding the acrylic oligomer in the range of 50 to 700 parts byweight relative to 100 parts by weight of acrylic polymer, while thenumber average molecular weight of the acrylic polymer is set at a valuewithin the range of 300,000 to 1,500,000, and the number averagemolecular weight of the acrylic oligomer is set at a value within therange of 1,000 to 10,000.